SUMMARY ? PATHOLOGY CORE The pathological assessment of old animals is important to determine whether the changes observed as animals age are associated with or independent of underlying pathological conditions. It is, therefore, essential to obtain accurate and thorough pathological assessments of aging animals. The Pathology Core will play a key role in the San Antonio Nathan Shock Aging Center because pathology increases exponentially with advancing age and is largely responsible for age-related morbidity and mortality. Knowledge of the pathological lesions associated with interventions used to study aging is essential to interpreting the impact of these interventions on the aging process(es). This knowledge will also provide insight into the underlying mechanism(s) behind the interventions' effects. The Pathology Core will build on the extensive experience of researchers at San Antonio and the expertise of the Core Leaders in pathological analyses of experimental animal models. Thus, the Specific Aims of the Pathology Core are: 1. To conduct comprehensive end-of-life and cross-sectional pathological analyses of established and new rodent models as well as other species used in aging research that die spontaneously or are sacrificed at specific age points in colonies maintained by the Aging Animal Models and Longevity Assessment Core. 2. To conduct immunohistochemical, molecular, and quantitative morphometric analyses of the tissues/organs of rodent models and other species by performing a) morphometric and immunohistochemical analyses on several lesions and age-related histological changes and b) in situ hybridization to further analyze the histological changes at the molecular level. 3. To continue to a) accrue a comprehensive database of histopathological data and images as a resource for analyses by investigators, b) provide basic pathological information for new investigations, and c) create a tissue archive by collecting and storing tissue samples (paraffin and frozen blocks) as a resource for analyses of samples as requested and for new morphological research. 4. To provide histopathology services for investigators by preparing paraffin and frozen blocks, making unstained slides, and performing various staining (including special staining). New services include (a) making tissue array slides for histological/morphological experiments, and (b) performing laser capture microdissection for further molecular analyses. 5. To assist faculty and students interested in the basic biology of animal models with the pathological analyses needed for grant applications and manuscript preparation.